Creating a georeferenced raster layer from an image

If you have an image file from a scanned map (for example, a historic map, or one you or a collaborator drew/annotated by hand), you can import it into GIS software and georeference it, which associates each pixel in your image with a geospatial location.

In QGIS, you may want to start by loading a basemap that you can use to identify locations on the map you’re georeferencing. You can add a basemap based on OpenStreetMap data by going to “Add Layer” from the “Layer” menu and selecting “Add XYZ layer.” In the dialog that comes up, you’ll be able to select “OpenStreetMap” from the dropdown menu. Then click the “Add” button

Now you can georeference your image. Select “Georeferencer…” from the layer menu.

In the georeferencer dialog, click the “Open Raster” button to load your image file. You’ll need to select at least three points on the image to georeference it. Ideally, there will be spaced far apart from one another (e.g. near the sides of the image) and will form a triangle (rather than being along a straight line).

Click the first point on your image. A box will pop up asking you for the coordinates of the point you’ve selected. Click the “From Map Canvas” button and find the corresponding location on in your map window. Click on the location and click okay.

Repeat this process for at least two more points. When you are satisfied with your control points, click the Settings button. Enter a filename for the georeferenced image and make sure the “Load in project when done” button is checked. Click Okay.

Click the “Start Georeferencing” button. When the process is finished, you can close the georeferencer dialog box. You’ll be prompted to save control points, which isn’t necessary.

Manually creating a layer of data

Once you’ve loaded a georeferenced layer, you might want to features to create a vector layer.

In QGIS, you’ll want to start by creating an empty shapefile. Go to Layer > Create Layer > New Shapefile Layer…

Select a filename and a geometry type, then click okay. The new, empty layer will be added to your map.

Now you’ll want to add features to your new layer. Right-click the layer you want to add to (probably the empty layer you just created) and select “Toggle Editing”. Then click the “Add points” button and click on map where you want your new points to be. When you are finished, save your edits and turn off the editing mode.